In the liquid crystal display technology, the Advanced Super Dimension Switch (ADS) technology mode gradually replaces the Twisted Nematic (TN) liquid crystal model due to the advantages, such as high transmittance, wide viewing angle, fast response speed and low power consumption, and becomes one of key technologies in the field of liquid crystal display.
In the ADS mode, an oxide thin film transistor has a protective layer 13 formed on an indium gallium zinc oxide (IGZO) layer where a channel is formed. FIG. 1 and FIG. 2 are a cross-sectional view and a top view of an oxide thin film transistor, respectively. In the oxide thin film transistor, the IGZO layer is connected with a source electrode 2 and a drain electrode 3 through via holes. Upon the via holes are formed, in order to prevent the source electrode 2 and the drain electrode 3 from short-circuiting, a certain interval is kept between the source electrode 2 and the drain electrode 3. An active layer in the interval is a channel 12 of the oxide thin film transistor, as indicated by L in FIG. 2. In the structure of the oxide thin film transistor, the length of the channel is generally within 9.5˜10 μm.